1. Field of the Invention
Embodiments disclosed herein relate generally to a method of manufacturing semiconductor devices and, more particularly, to a method of manufacturing semiconductor devices, including a process of forming mask patterns.
2. Description of the Related Art
A semiconductor device is formed by a plurality of processes of forming mask patterns. The process of forming mask patterns may include depositing a mask layer and removing the selected region of the mask layer. The mask layer may be a photoresist layer or may be a layer patterned by a photolithography process. If the mask layer is a photoresist layer, a photolithography process may be performed to remove selected regions of the mask layer in order to form mask patterns. The photolithography process includes a process of forming the photoresist layer, an exposure process for the selected region of the photoresist layer, a development process of removing the exposed region or the non-exposed region of the photoresist layer, and a cleaning process. The photolithography process may form the photoresist pattern is formed. The photoresist pattern may play the role of an etch mask or may be used as mask patterns in an etch process for removing the selected region of the mask layer. The mask patterns may play the role of an etch mask in an etch process for removing the selected region of a specific layer or may play the role of an impurity implantation mask in an impurity implantation process.
The mask patterns may be part of a region where a plurality of patterns is formed that may create openings. When openings are formed within a plurality of patterns, some or all of the plurality of patterns may collapse or incline.
FIGS. 1A and 1B are cross-sectional views illustrating a prior art process of forming mask patterns comprising openings, where the formation of the openings may lead to collapsed or inclined patterns.
Referring to FIG. 1A, a plurality of spaced patterns 3 is formed over a semiconductor substrate 1. A mask layer 5 is formed on the entire structure in which the plurality of patterns is formed. An example where the mask layer 5 is a photoresist layer is described below for convenience of description.
Referring to FIG. 1B, after the selected region of the photoresist layer 5 is exposed, depending on whether the photoresist is a positive or negative type, either the exposed region or the non-exposed region of the photoresist layer 5 is removed using a developer. A cleaning process is then performed to form a mask pattern (that is, a photoresist pattern 5a) through which the region where the plurality of patterns 3 is formed is opened. If the photoresist layer 5 is a positive type, the exposed region of the photoresist layer 5 is removed. If the photoresist layer 5 is a negative type, the non-exposed region of the photoresist layer 5 is removed.
When the exposed region or the non-exposed region of the photoresist layer 5 is removed, a developer dissolves the exposed region or the non-exposed region of the photoresist layer 5. The developer is filled in an interval or space between the patterns 3 in a region from which the photoresist layer will be removed and then discharged. In the process of removing the photoresist, the patterns 3 may collapse or incline because of interfacial tension generated by the application of the developer.
Furthermore, if wet cleaning using a cleaning agent is performed after forming the photoresist pattern 5a, the cleaning agent is filled in the interval between the patterns 3 and then discharged. The patterns 3 may be collapse or incline because of interfacial tension created by the cleaning agent.
The plurality of patterns 3 may be cell gates of a NAND flash memory device. The photoresist pattern 5a may be an impurity implantation mask for blocking regions other than a memory cell region. The cell gates may be formed in a subsequent process of forming cell junctions by implanting impurities into the semiconductor substrate 1 between the cell gates.
As described above, the phenomenon in which the patterns 3 inclines or collapses typically occurs when the aspect ratio of each of the patterns 3 becomes 10:1 or higher. Revolution per minute (RPM) may be reduced when the developer or the cleaning agent is discharged, but to prevent incline or collapse of the patterns, changing the RPM when cleaning or developing leads to insubstantial improvement.